Learning objectives
The aim of the course is to present and discuss an organic class of transport phenomena in the condensed matter. The choice is oriented to electronic transport in semiconductors due to a rich available phenomenology, also in the field of low dimensional structures.
Prerequisites
The knowledge of elements of solid state physiscs are recommended, therefore the courses of "Introduction to Solid State Physics" and "Statistical Physics" should be previously attended.
Course unit content
ELETTRONIC TRASPORT IN SEMICONDUCTORS<br />
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<u>General properties of semiconductors</u><br />
Energy band structures: direct and indirect energy gap. Effective masses of electrons and holes. Impurity levels. Shallow impurities in the effective mass approximation. Deep levels. Equilibrium statistics of electrons and holes. Temperature and doping dependence of the Fermi energy. Intrinsic and exhaustion regimes. Low temperature freezing of carriers. Compensation mechanisms; the case of semi-insulating GaAs.<br />
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<u>Introduction to transport phenomena</u><br />
Bloch oscillations and collision processes. The Boltzmann equation. The collision integral in the relaxation time approximation. Electrical conductivity in the ohmic regime: spherical and ellipsoidal energy surfaces. Scattering processes. Ionized impurity scattering and phonon scattering. Transport phenomena in the particle kinetic model.<br />
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<u>Magneto-transport</u><br />
Electron in a magnetic field. Landau quantization and level degeneracy. Cyclotron resonance of electrons and holes. Classical magneto-transport. Hall effect and physical magneto-resistance. Geometrical magneto-resistance. Quantum magneto-transport. Orbit and flux quantization. The Shubnikov de Haas effect. The extreme quantum limit. The 2D electron gas and the quantum Hall effect. The ballistic regime: quantization of the electrical conductance in 1D systems.<br />
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<u>Transport of excess carriers</u><br />
Space charge and dielectric relaxation. Generation and recombination of carriers. Lifetime of excess carriers. Space-time evolution of non-equilibrium electrons and holes. Continuity equation of currents. The ambipolar equation. Stationary solutions of the ambipolar equation: injection and extraction of minority carriers. Time dependent solutions: the Haynes-Shockley experiment. Application to the case of the charge transport in the p/n junction.
Full programme
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Bibliography
Notes by the teacher
Teaching methods
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Assessment methods and criteria
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Other information
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